Multi-layer pile casing pile pulling process in complex environment

Abstract

The invention relates to a multi-layer pile casing pile pulling process in a complex environment. The multi-layer pile casing pile pulling process comprises the steps of surveying and setting out to determine the position of a pile foundation to be pulled, excavating and sinking a large-diameter steel casing, pouring waterproof concrete, pre-burying a casing opening water stop device, sinking a small-diameter steel casing, fixing the small-diameter steel casing, sinking a pile pulling casing, pulling a pile and removing obstacles, and backfilling and repairing a structure. The large-diameter steel casing is located on the outermost periphery of a pile pulling obstacle clearing point. The small-diameter steel casing is positioned on the inner side of the large-diameter steel casing; the cast-in-place concrete is used for sealing and fixing the joint of the steel casing and the existing structure; the pile pulling protection cylinder is located on the inner side of the small-diameter steel protection cylinder. Under the environment of complex peripheral buildings, pile pulling and obstacle removing operation from the ground to the area below the existing buildings can be completed, and the influence on the underground existing buildings is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to a multi-layer casing pile extraction process applicable to complex surrounding building environments. Background Technology

[0002] With the rapid development of urban construction, the land area required for municipal construction projects is constantly decreasing, and the focus is shifting rapidly towards underground engineering. Urban underground engineering is intricate and complex. As underground space is continuously developed, conflicts often arise between new facilities and existing foundations during construction. If old foundations are not removed in a timely manner, they may pose a threat to the safety of new projects and surrounding facilities. Residual parts of old foundations may damage construction equipment or even cause safety accidents.

[0003] Therefore, the removal of old piles is necessary before constructing new underground projects. However, considering the actual conditions of the project, traditional pile removal techniques have many problems:

[0004] I. Removing piles and clearing obstacles inside existing buildings and structures:

[0005] 1) Some existing underground structures have low internal clearance and insufficient space for pile removal and obstacle clearing, making conventional construction techniques unusable and requiring special construction techniques and processes, which are costly; 2) The overall construction period is relatively long; 3) There is a problem of sudden gushing of pressurized water; 4) It occupies a large amount of construction space, and if it is an existing underground tunnel, it will have a significant impact on traffic inside the tunnel and may even affect the existing internal structure of the tunnel.

[0006] II. Ground pile removal and obstacle clearing:

[0007] 1) It affects the internal traffic flow of existing buildings and structures; 2) It requires penetrating existing underground buildings and structures, which causes significant structural damage, and the temporary waterproofing requirements for the structure are high during the pile extraction process.

[0008] In existing related technologies, such as patent document (CN102644274A), a method for constructing retaining piles through existing structures is disclosed. Its core is to assist in hole formation by using steel casing. However, this technology is aimed at "pile formation" rather than "pile extraction". The steel casing is only a single layer and does not have a special water-stopping structure, which cannot solve the problem of clearing obstacles and waterproofing during pile extraction. Patent document (HK1150416A) discloses a single-casing pile extraction method that relies on circular wedges to cut the pile body. However, its single-layer casing design has poor adaptability to multi-layer complex structures and does not consider the waterproof sealing requirements of existing buildings and structures, which can easily lead to water leakage and structural disturbance.

[0009] Therefore, the traditional pile extraction method has begun to show its drawbacks, and there is an urgent need to optimize, innovate, transform or design a new pile extraction and obstacle removal process that is suitable for complex environments, based on actual engineering conditions. Summary of the Invention

[0010] The present invention provides a multi-layer casing pile extraction process suitable for complex environments. It can complete the pile extraction and obstacle removal operation from the ground to the area below existing buildings and structures in complex surrounding environments, meeting the requirements of relatively short construction period, minimal impact on existing underground buildings and structures, and effective reduction of water leakage risk during pile extraction.

[0011] To achieve the above objectives, the technical solution of the present invention is: a multi-layer casing pile extraction process in a complex environment, comprising the following steps: (1) measuring and setting out to determine the location of the pile foundation to be extracted; (2) excavating and sinking a large-diameter steel casing, the large-diameter steel casing being located at the outermost periphery of the pile extraction and obstacle clearing point, with its bottom end sinking to the top slab of the existing building; (3) pouring waterproof concrete at the joint between the large-diameter steel casing and the top slab of the existing building to achieve sealing and fixation; (4) pre-embedding a water-stopping device at the casing opening in the bottom slab of the existing building; (5) sinking a small-diameter steel casing, the small-diameter steel casing being located at the top slab of the large-diameter steel casing. (6) Fix the small-diameter steel casing; (7) Sink the pile extraction casing, which is located inside the small-diameter steel casing, penetrates the top and bottom slabs of the existing building, and sinks into the pile extraction and obstacle removal area; (8) Carry out pile extraction and obstacle removal construction through the pile extraction casing; (9) Remove the casing, first pull out the innermost pile extraction casing, backfill with thick grout while pulling out the casing, and then remove the small-diameter steel casing and the large-diameter steel casing in sequence; (10) Backfill and repair the structure, and use cast-in-place concrete to seal and repair the opening positions of the existing building.

[0012] Furthermore, in step (1), the surveying and setting out are carried out on the ground and within existing buildings to determine the specific location of the pile foundation to be removed.

[0013] Furthermore, based on the measurement and layout points and the dimensions of the small-diameter steel casing, the location and dimensions of the pre-embedded casing water-stop device are determined.

[0014] Furthermore, in step (3), a rubber waterstop strip is first inserted at the joint between the large-diameter steel casing and the top slab of the existing building, and then waterproof concrete is poured to seal and fix it.

[0015] Furthermore, in step (4), a hole is first made at the top plate of the existing building, and a small-diameter steel sleeve is installed and sunk into the bottom plate of the existing building. The bottom outer side of the small-diameter steel sleeve and the joint between the bottom plate are sealed and fixed by a water-stopping device.

[0016] Furthermore, in step (4), the cylinder nozzle water-stopping device consists of a flange, a cylinder nozzle steel pipe, a bypass valve, a steel plate, and expansion bolts, and is used to seal and fix the joint between the small-diameter steel casing and the bottom plate of the existing underground building.

[0017] Furthermore, the water-stopping device at the cylinder opening is connected to the existing building's base structure by welding steel plates and installing expansion bolts. It is fixed with flanges and connected to the small-diameter steel casing by welding steel plates. Grouting is used to fill the annular space between the cylinder opening steel pipe and the small-diameter steel casing.

[0018] Furthermore, in step (6), the small-diameter steel casing is fixed by welding steel plates and installing expansion bolts to seal and fix the joint between the small-diameter steel casing and the top plate of the existing building, and a water-stop device at the casing mouth is used to seal and fix the joint between the small-diameter steel casing and the bottom plate of the existing building.

[0019] Furthermore, in step (6), grout is injected into the annular space between the steel pipe at the cylinder opening and the small-diameter steel casing through the bypass valve. The grouting material is first a single-liquid grout with a water-cement ratio of 0.8:1, and then a double-liquid grout with a cement grout and water glass volume ratio of 1:1. The grouting pressure is no more than twice the water and soil pressure at the bottom slab of the existing building.

[0020] Furthermore, in step (10), after the pile extraction and obstacle removal construction is completed, thick grout is used to backfill the pile hole, and the innermost pile extraction sleeve is pulled out while backfilling; then the inner small-diameter steel casing is removed, and the existing building's bottom slab opening position is treated by planting reinforcement bars, laying waterstop strips, and pouring waterproof concrete to seal the hole; finally, a scaffold is erected, and the existing building's top slab opening position is treated by planting reinforcement bars, pouring waterproof concrete to seal the hole, and backfilling the excavated area above, thus ending the backfilling and repair work.

[0021] The process of the present invention has the following beneficial effects:

[0022] 1) It requires little space for construction operations, has minimal impact on traffic, and is adaptable to a wide range of scenarios;

[0023] 2) It has minimal impact on existing buildings and structures in the surrounding area;

[0024] 3) Excellent waterproof sealing, ensuring high safety during the pile removal and obstacle clearing process;

[0025] 4) The process is simple, the process materials can be reused, and it can be promoted and utilized.

[0026] 5) The pile extraction technology is mature and the construction period is relatively short. Attached Figure Description

[0027] Figure 1 This is a field schematic diagram of the multi-layer casing pile extraction process applicable to complex environments according to the present invention;

[0028] Figure 2 This is a schematic diagram of the excavation and sinking stage of the outer large-diameter steel casing, which is a process flow node of the present invention.

[0029] Figure 2(a) is a schematic diagram of the cast-in-place waterproof concrete on the upper part of the small-diameter steel casing;

[0030] Figure 3 This is a schematic diagram of the sinking stage of the inner small-diameter steel casing, which is a process flow node of the present invention.

[0031] Figure 3 (a) is a schematic diagram of the welding connection of the upper steel plate of the small-diameter steel casing;

[0032] Figure 3 (b) is a schematic diagram of the water-stopping device at the cylinder opening;

[0033] Figure 4 This is a schematic diagram of the pile removal and obstacle clearing stage in the process flow of this invention.

[0034] Figure 5 This is a schematic diagram of the backfilling and repair structure stage in the process flow of this invention;

[0035] In the diagram: 1-Pile extractor, 2-Large diameter steel casing, 3-Small diameter steel casing, 4-Water-stop device at the casing opening, 5-Pile extraction casing, 6-Pile to be extracted, 7-Cast-in-place concrete, 8-Rubber waterstop strip, 9-Steel plate, 10-Expansion bolt, 11-Flange, 12-Steel pipe at the casing opening, 12-Bypass valve. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] like Figure 1 As shown in the figure, the present invention provides a multi-layer casing pile extraction process suitable for complex environments. The process flow is as follows: measuring and setting out to determine the location of the pile foundation to be extracted, excavating and sinking a large-diameter steel casing 2, pouring waterproof concrete, pre-embedding a water-stopping device 4 at the casing opening, sinking a small-diameter steel casing 3, fixing the small-diameter steel casing 3, sinking the pile extraction casing 5, pile extraction and obstacle removal construction, removing the casing, and backfilling to repair the structure.

[0038] like Figure 2 As shown: First, the ground and existing buildings are surveyed and laid out to accurately locate the specific position of the pile to be removed. Then, a large-diameter steel casing is excavated and driven into the top slab of the existing building. The joint between the inner side of the bottom of the large-diameter steel casing and the top slab is sealed and fixed with cast-in-place concrete.

[0039] like Figure 2 As shown in (a): a rubber waterstop strip 8 is first inserted at the joint between the large-diameter steel casing 2 and the top slab of the existing building, and then waterproof concrete 7 is poured to seal and fix it.

[0040] like Figure 3As shown: Based on the surveyed and laid-out points and the dimensions of the small-diameter steel casing, determine the location and dimensions of the pre-embedded casing waterstop device. The casing waterstop device is pre-embedded within the existing building's foundation slab. An opening is made at the location of the existing building's top slab, and a small-diameter steel casing is installed and sunk into the existing building's foundation slab. The location of the joint between the outer side of the bottom end of the small-diameter steel casing and the foundation slab (see...) Figure 3 (a) Use a water-stop device at the cylinder mouth for waterproof sealing and fixation.

[0041] like Figure 3 As shown in (b): The cylindrical water-stop device 4 consists of a flange 11, a cylindrical steel pipe 12, a bypass valve 13, a steel plate 9, and expansion bolts 10. To embed the cylindrical water-stop device 4, the internal structure and protective layer of the existing building's base slab must first be removed, allowing the bottom of the cylindrical water-stop device 4 and the expansion bolts 10 to be embedded within the structure. After the small-diameter steel casing 3 is inserted into the cylindrical water-stop device 4 and lowered to the existing building's base slab, the lower end of the cylindrical steel pipe 12 is connected to the existing building's base slab structure by welding the steel plate 9 and installing the expansion bolts 10. The upper end of the cylindrical steel pipe 12 is connected to the small-diameter steel casing 3 by fixing with the flange 11 and welding with the steel plate 9.

[0042] Then, the pre-reserved bypass valve 13 next to the cylindrical steel pipe 12 is used to grout the annular space between the cylindrical steel pipe 12 and the small-diameter steel casing 3, and the grouting pressure and grouting volume are controlled simultaneously. The grouting pressure meets the grouting requirements and is not greater than twice the water and soil pressure at the foundation slab of the existing building. During grouting, a single-component grout (water-cement ratio 0.8:1) should be injected first, followed by a double-component grout (water-cement ratio 1:1, cement grout: water glass 1:1). The grouting volume is determined according to the volume of the annular space and the requirements of the project site. After grouting is completed, the next step of construction can only be carried out after observing that there is no leakage at the bypass valve and the flange of the cylindrical pipe (observation should be carried out for no less than 12 hours after single-component grouting and no less than 2 hours after double-component grouting).

[0043] like Figure 4 As shown: A construction platform is set up on the ground, the pile extractor is positioned, and the pile extraction steel sleeve is sunk into the small-diameter steel casing. The sleeve passes through the existing building's base slab to the pile extraction area to carry out pile extraction and obstacle removal work.

[0044] like Figure 5 As shown: After completing the pile extraction and obstacle removal work, thick grout was used to backfill the pile hole, and the innermost pile extraction sleeve was pulled out while backfilling; then the inner small-diameter steel casing was removed, and the opening positions of the existing building's bottom slab were treated by planting rebar, laying waterstop strips, and pouring waterproof concrete to seal the holes; finally, a scaffold was erected, and the opening positions of the existing building's top slab were treated by planting rebar, pouring waterproof concrete to seal the holes, and backfilling the excavated area above, thus completing the backfilling and repair work and the entire multi-layer casing pile extraction process in a complex environment.

[0045] This invention is applied to a new subway tunnel project in a city that passes under an existing highway tunnel. This project abandoned the traditional pile extraction process with low clearance conditions within the existing tunnel, and instead adopted the multi-layer casing pile extraction process of this invention under complex conditions. During the pile extraction process, the impact on traffic within the tunnel is minimal, the disturbance to the internal tunnel structure is small, the construction process has good waterproofing and sealing performance, high safety, and a relatively short overall construction period.

Claims

1. A multi-layer casing pile extraction process under complex environments, characterized in that, Includes the following steps: (1) Measure and set out the location of the pile to be extracted; (2) Excavate and sink a large-diameter steel casing, which is located at the outermost edge of the pile extraction and obstacle clearing point, with its bottom end sinking to the top slab of the existing building; (3) Pour waterproof concrete at the joint between the large-diameter steel casing and the top slab of the existing building to achieve sealing and fixation; (4) Pre-embed a water-stop device at the casing opening in the bottom slab of the existing building; (5) Sink a small-diameter steel casing, which is located inside the large-diameter steel casing, penetrates the top slab of the existing building, and has its bottom end sinking to the top slab of the existing building. (6) Fix the small-diameter steel casing; (7) Sink the pile extraction casing, which is located inside the small-diameter steel casing, penetrating the top and bottom slabs of the existing building structure, and sinking it into the pile extraction and obstacle removal area; (8) Carry out pile extraction and obstacle removal construction through the pile extraction casing; (9) Remove the casing, first pull out the innermost pile extraction casing, backfill with thick grout while pulling out the casing, and then remove the small-diameter steel casing and the large-diameter steel casing in sequence; (10) Backfill and repair the structure, and use cast-in-place concrete to seal and repair the openings of the existing building structure.

2. The multi-layer casing pile extraction process under complex environments according to claim 1, characterized in that, In step (1), the surveying and setting out are carried out on the ground and within existing buildings to determine the specific location of the pile foundation to be removed.

3. The multi-layer casing pile extraction process under complex environments according to claim 2, characterized in that, Based on the measurement and layout points and the dimensions of the small-diameter steel casing, determine the location and dimensions of the pre-embedded casing water-stop device.

4. The multi-layer casing pile extraction process under complex environments according to claim 1, characterized in that, In step (3), a rubber waterstop strip is first inserted at the joint between the large-diameter steel casing and the top slab of the existing building, and then waterproof concrete is poured to seal and fix it.

5. The multi-layer casing pile extraction process under complex environments according to claim 1, characterized in that, In step (4), a hole is first made at the top plate of the existing building, and a small-diameter steel sleeve is installed and sunk into the bottom plate of the existing building. The bottom outer side of the small-diameter steel sleeve and the joint of the bottom plate are sealed and fixed with a water-stopping device.

6. The multi-layer casing pile extraction process under complex environments according to claim 1, characterized in that, In step (4), the cylinder nozzle water-stopping device consists of a flange, a cylinder nozzle steel pipe, a bypass valve, a steel plate and expansion bolts, and is used to seal and fix the joint between the small diameter steel casing and the bottom plate of the existing underground building.

7. The multi-layer casing pile extraction process under complex environments according to claim 6, characterized in that, The water-stopping device at the cylinder opening is connected to the existing building's base structure by welding steel plates and installing expansion bolts. It is fixed with flanges and connected to the small-diameter steel casing by welding steel plates. Grouting is used to fill the annular space between the cylinder opening steel pipe and the small-diameter steel casing.

8. The multi-layer casing pile extraction process under complex environments according to claim 1, characterized in that, In step (6), the small-diameter steel casing is fixed by welding steel plates and installing expansion bolts to seal and fix the joint between the small-diameter steel casing and the top plate of the existing building. A water-stop device at the casing mouth is used to seal and fix the joint between the small-diameter steel casing and the bottom plate of the existing building.

9. The multi-layer casing pile extraction process under complex environments according to claim 6, characterized in that, In step (6), grout is injected into the annular space between the steel pipe at the cylinder opening and the small-diameter steel casing through the bypass valve. The grouting material is first a single liquid grout with a water-cement ratio of 0.8:1, and then a double liquid grout with a cement grout and water glass volume ratio of 1:

1. The grouting pressure is no more than twice the water and soil pressure at the bottom slab of the existing building.

10. The multi-layer casing pile extraction process under complex environments according to claim 1, characterized in that, In step (10), after the pile extraction and obstacle removal work is completed, thick grout is used to backfill the pile hole, and the innermost pile extraction sleeve is pulled out while backfilling; then the inner small-diameter steel casing is removed, and the existing building's bottom slab opening position is treated by planting rebar, laying waterstop strips, and pouring waterproof concrete to seal the hole; finally, a scaffold is erected, and the existing building's top slab opening position is treated by planting rebar, pouring waterproof concrete to seal the hole, and backfilling the excavated area above, thus ending the backfilling and repair work.

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